Investigation On Burning Behaviors Of Pool Fire In Ceiling Vented Compartment Under Ambient Cross Wind

The vigorous development of the maritime transportation industry has made the issue of ship fire safety increasingly prominent.According to accident statistics,most ship fires occur in the engine rooms,and more than 70 percent of ship fire accidents occurred during sea navigation.Ships sailing at sea will inevitably be affected by sea wind,and the accident reports showed that ship fire under the influence of wind was more harmful.The previous researchers modeled ship cabin as ceiling vented compartment for fire research,while rarely took the cross wind effect into consideration.Therefore,studying the ceiling vented compartment fire under the effect of cross wind could provide theoretical reference for the prevention of such ship fire and the formulation of emergency rescue countermeasures.In this paper,the burning behaviors of the pool fire inside the ceiling vented compartment under the ambient cross wind were experimentally studied.The influence of the pool diameter,opening size and cross wind velocity on the burning characteristic parameters and self-extinction behavior of pool fire inside the ceiling vented compartment were revealed.Based on the heat balance and energy conservation,prediction models of the fire heat release rate,the heat loss from the top opening and the temperature rise were established.The main work includes:(1)Investigation on the burning characteristics of pool fire inside the ceiling vented compartment under ambient cross windThe variation laws of the pool fire burning rate,burning duration and temperature distribution inside the compartment in the windy environment were investigated by changing the pool diameter,opening size and cross wind velocity.The results showed that the burning rate increased and the burning duration decreased gradually with the increasing of the opening size,and the cross wind effect on the burning rate and burning duration of the pool fire inside the compartment was not obvious under the same opening size.The temperature distribution in the ceiling vented compartment changed with the increasing of the cross wind velocity.The temperature of the windward side was higher than that of the leeward side when the cross wind velocity was small,and then gradually became lower than the leeward side as the cross wind velocity increased.When the compartment top was fully open,the experimental results showed that the flame changed from tilting to the windward side to tilting to the leeward side as the cross wind velocity increased.Based on the dimensional analysis,the relationship between the critical conditions for the flame tilt transition and the cross wind velocity,fire heat release rate and cabin characteristic parameters was obtained,and an empirical formula for predicting the critical cross wind velocity of flame tilt transition was proposed.(2)Investigation on the self-extinction behavior of pool fire inside the ceiling vented compartment under ambient cross windAccording to the burning behavior of the pool fire under different cross wind velocities and top opening sizes,the effect of cross wind velocity and opening size on self-extinction behavior were obtained.The relationship between the oxygen mass change rate and self-extinction behavior in the compartment was analyzed based on the conservation of components under both the self-extinction condition and free-burning condition.It was found that compared with free-burning conditions,the reduction rate of oxygen concentration in the compartment was larger in the cases of self-extinction,and the reduction rate of oxygen concentration under the effect of cross wind was lower than that in the windless environment.The influence of the opening size and the cross wind velocity on the reduction rate of the oxygen concentration inside the compartment was comprehensively analyzed,and an Empirical model of the oxygen concentration reduction rate coupled with the opening size and the cross wind velocity were produced.By analyzing the relationship between gas flow at the top opening and pressure and thermal buoyancy,a calculation method for the prediction parameter SE of the critical condition for the self-extinction of the pool fire inside the ceiling vented compartment in the windless environment was proposed.A prediction model for the critical oxygen concentration of pool fire self-extinguishing in the ceiling vented compartment in the windy environment was established based on the adiabatic flame temperature.(3)The development of prediction models for fire parameters inside the ceiling vented compartment under ambient cross windThe thermal balance analysis of the ceiling vented compartment fire was carried out based on the energy conservation,and the effect of the cross wind on the burning parameters of the fire inside the ceiling vented compartment was deeply analyzed.The relationships between the fire burning rate and the gas flow rate at the opening and the cross wind velocity was theoretically analyzed,and a dimensionless top-opening ventilation factor coupling opening size,fire diameter and cross wind velocity was proposed.The fire parameters of the ceiling vented compartment fire were analyzed using the top-opening ventilation factor.Prediction models of fire heat release rate and top opening heat loss were established related to the top opening ventilation factor.Based on the analysis of energy conservation and the empirical model of the gas flow rate at the top opening,a dimensionless temperature rise prediction model in the ceiling vented compartment under the effect of cross wind was established.